Surfboards moved by user power

ABSTRACT

Surfboards moved by user power comprises: a surfboard body streamlined, when viewed from a plan view, concave grooves are formed on both sides, respectively; a propulsion body including: a first propulsion body formed with a first propulsion unit that is hinged to one side groove of the surfboard body and is formed inclined with respect to the surfboard body on a lower surface to generate propulsion force according to the movement of the user&#39;s feet; and a second propulsion body formed with a second propulsion unit that is hinged to the other side groove of the surfboard body and is formed inclined with respect to the surfboard body on a lower surface to generate propulsion force according to the movement of the user&#39;s feet; and a direction change unit including: a rotating shaft passing through the surfboard body; a handle disposed on an upper end of the surfboard body of the rotating shaft to rotate the rotating shaft; and a direction change key that is disposed on a lower part of the surfboard body of the rotating shaft and rotates together with the rotating shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT International Application No.PCT/KR2020/018682 filed on Dec. 18, 2020, which application claimspriority to Korean Patent Application No. 10-2020-0100622 filed on Aug.11, 2021, the entire disclosures of which are expressly incorporatedherein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND Technical Field

The present invention relates to a surfboard, and more particularly, toa surfboard that can be moved by a user's power on a calm shore withoutwaves and whose direction also can be changed by using user's handsduring movement.

Background Art

In general, surfing is a marine sport that competes for height, speed,and skill by riding a surfboard up and down the slope surface of seawaves, and it is a sport that requires a high sense of balance andprecise timing.

To enjoy surfing, there must be waves, and if there are no waves in thesea, you cannot enjoy surfing.

For enjoying surfing in the sea without waves, in Korean PatentPublication No. 2003-0067609, Motor Surfing Board (published on Aug. 14,2003), a technology that allows you to enjoy surfing in a place wherethere is no wind or waves by attaching a power device that uses a motorto the surfboard has been disclosed.

However, when a motor and the like is mounted on a surfboard to enjoysurfing in a place where there is no wind or waves, since in addition tothe motor, various components such as a battery that delivers power torun the motor must be mounted on a very small surfboard, it is not easyto implement and has a problem in that the manufacturing cost isexcessively increased.

BRIEF SUMMARY Technical Subject

The present invention provides surfboards moved by user power that canbe moved by a user's power on a shore without winds or waves and whosedirection also can be easily changed by using user's hands duringmovement, and after use, each part is folded to enhance the convenienceof movement and minimize the storage volume.

Technical Solution

As an embodiment, surfboards moved by user power comprise: a surfboardbody streamlined, when viewed from a plan view, concave grooves areformed on both sides, respectively; a propulsion body including: a firstpropulsion body formed with a first propulsion unit that is hinged toone side groove of the surfboard body and is formed inclined withrespect to the surfboard body on a lower surface to generate propulsionforce according to the movement of the user's feet; and a secondpropulsion body formed with a second propulsion unit that is hinged tothe other side groove of the surfboard body and is formed inclined withrespect to the surfboard body on a lower surface to generate propulsionforce according to the movement of the user's feet; and a directionchange unit including: a rotating shaft passing through the surfboardbody; a handle disposed on an upper end of the surfboard body of therotating shaft to rotate the rotating shaft; and a direction change keythat is disposed on a lower part of the surfboard body of the rotatingshaft and rotates together with the rotating shaft.

It further comprises: an overturn prevention body having a firstprevention body hinged to one side of the front end part of an uppersurface of the surfboard body of the surfboards moved by user power andat a different height from the first propulsion body; and a secondoverturn prevention body hinged to the other side of a front end part ata different height from the first propulsion body, wherein the first andsecond overturn prevention bodies are coupled to the upper surface ofthe surfboard body, and wherein the first and second propulsion bodiesare formed at the same height as the side surface of the surfboard body.

The first and second propulsion bodies of the surfboard moved by userpower are hinged in a ball-socket joint method that freely moves withrespect to the surfboard body, and through holes are formed in the firstand second overturn prevention bodies, and the through holes areinserted into the protrusions protruding from the upper surface of thesurfboard body so that the first and second overturn prevention bodiesare rotated in a direction parallel to the upper surface of the surfaceboard body.

The direction change unit of surfboards moved by user power comprises: athrough hole passing through the surfboard body; a rotating memberinserted into the through hole and rotated in a direction parallel tothe surfboard body; a first folding part coupled to the rotating shafton an upper portion of the rotating member to fold the rotating shaft;and a folding unit having a second folding part for folding thedirection change key on a lower portion of the rotating member.

A first coupling portion that is separated or coupled to the side of thesurfboard body is formed in the first and second propulsion bodies ofsurfboards moved by user power, a second coupling portion separated orcoupled to the first coupling portion is formed on the side of thesurfboard body, a third coupling portion coupled to the upper surface ofthe surfboard body is formed in the first and second overturn preventionbodies, a fourth coupling portion coupled to the third coupling portionis formed on the upper surface of the surfboard body.

The overturn prevention body of surfboards moved by user power furthercomprises: a third overturn prevention body that is hinged at adifferent height from the first propulsion body on one side of the rearend part opposite to the front end part of the upper surface of thesurfboard body; and an overturn prevention body having a fourth overturnprevention body hinged to the other side of the rear end part at adifferent height from the first propulsion body, wherein through holesare formed in the third and fourth overturn prevention bodies, and thethrough holes are inserted into the protrusions protruding from theupper surface of the surfboard body, and the third and fourth overturnprevention bodies are rotated in a direction parallel to the uppersurface of the surfboard body.

Advantageous Effects

The surfboards moved by user power according to the present inventioncan be moved by the user's power on the coast where there are no windsor waves, and the direction can be easily changed using the user's handduring movement, and have an effect that after use, each part can befolded to enhance the convenience of moving and minimize the storagevolume.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is an external perspective view of surfboards moved by user poweraccording to an embodiment of the present invention.

FIG. 2 is a front view in the A direction of FIG. 1 .

FIG. 3 is a cross-sectional view illustrating a ball socket joint of thefirst and second propulsion bodies illustrated in FIG. 1 .

FIG. 4 is a cross-sectional view illustrating a direction change unit.

FIG. 5 is a cross-sectional view illustrating the coupling of anoverturn prevention body and a surfboard body according to an embodimentof the present invention.

FIG. 6 is an external perspective view of surfboards moved by user poweraccording to another embodiment of the present invention.

DETAILED DESCRIPTION

The present invention described hereinafter can apply varioustransformations and can have various embodiments, and specificembodiments are illustrated in the drawings and described in detail inthe detailed description.

However, this is not intended to limit the present invention to specificembodiments, and it should be understood that all modifications,equivalents and substitutes included in the spirit and scope of thepresent invention are included. In describing the present invention, ifit is determined that a detailed description of a related knowntechnology may obscure the gist of the present invention, the detaileddescription thereof will be omitted.

The terms used in the present application are only used to describespecific embodiments, and are not intended to limit the presentinvention. The singular expression includes the plural expression unlessthe context clearly dictates otherwise. In the present application, itshould be understood that terms such as “comprise” or “have” areintended to designate that a feature, number, step, operation,component, part, or combination thereof described in the specificationexists, but this does not preclude the possibility of addition orexistence of one or more other features or numbers, steps, operations,components, parts, or combinations thereof.

In addition, terms such as first, second, and the like may be used todistinguish and describe various components, but the components shouldnot be limited by the above terms. The above terms are used only for thepurpose of distinguishing one component from another.

In addition, when at least two different embodiments are described inthe present application, all or part of the components may be used bymerging and interchangeably using with each other, even if there is noparticular description within the scope not departing from the technicalspirit of the present invention.

FIG. 1 is an external perspective view of surfboards moved by user poweraccording to an embodiment of the present invention. FIG. 2 is a frontview in the A direction of FIG. 1 .

Referring to FIGS. 1 and 2 , a surfboard 600 includes a surfboard body100, a propulsion body 200, and a direction change unit 300. In additionto this, the surfboard 600 may further include an overturn preventionbody 400.

The surfboard body 100 serves as a base for supporting or fixing thepropulsion body 200, the direction change unit 300 and the overturnprevention body 400.

The surfboard body 100 may be made of a variety of highly rigidmaterials so as to be floated in water.

The surfboard body 100 may be formed, for example, in a streamlinedshape, a spindle shape, an aerodynamic shape, or a rectangular shape,and the like, and concave grooves 110 may be formed on both sides of thesurfboard body 100, respectively.

In one embodiment of the present invention, the shape of the concavegrooves 110 respectively formed on both sides of the surfboard body 100may be formed in a shape corresponding to the propulsion body 200, whichwill be described later, when viewed in a plan view.

The propulsion body 200 is coupled to the surfboard body 100. Thepropulsion body 200 makes it possible to move the surfboard body 100 bypurely using the user's power, not the power generated by a motor.

The propulsion body 200 includes a first propulsion body 210 and asecond propulsion body 260.

The first propulsion body 210 is formed in a rectangular shape, thefirst propulsion body 210 is disposed in a concave groove 110 formed onthe side of the surfboard body 100, and the first propulsion body 210 isformed in a shape in close contact with a groove 110.

The first propulsion body 210 may, for example, be formed in arectangular shape or a streamlined shape, and the first propulsion body210 may be formed in a width suitable for placing a user's foot.

A strap 215 for preventing the user's feet from being separated may beformed on the upper surface of the first propulsion body 210, and ananti-slip pad and the like for preventing the user's feet from slippingmay be placed on the upper surface of the first propulsion body 210.Unlike this, a concave separation prevention groove may be formed in aportion of the upper surface of the first propulsion body 210corresponding to the strap 215 so that the user's foot does not slip.

In one embodiment of the present invention, preventing the user's footfrom being separated from the upper surface of the first propulsion body210 is because propulsion force is generated through a motion in whichthe user spreads or narrows the first propulsion body 210 in thehorizontal direction on the water surface, a motion in which the firstpropulsion body 210 is elevated and descended up and down with respectto the surfboard body 100, and a motion in which the first propulsionbody 210 is rotated from left to right with respect to the surfboardbody 100, and the like, and at this time, the user's foot can be easilyseparated from the first propulsion body 210.

In one embodiment of the present invention, a ball 216 is formed at thefront end portion of the first propulsion body 210 to enable the user toperform the motion of widening or narrowing the first propulsion body210 in the horizontal direction on the water surface, the motion ofelevating the first propulsion body 210 up and down with respect to thesurfboard body 100, and the motion of rotating the first propulsion body210 left and right with respect to the surfboard body 100.

FIG. 3 is a cross-sectional view illustrating a ball socket joint of thefirst and second propulsion bodies illustrated in FIG. 1 .

Referring to FIGS. 1 to 3 , a concave groove 112 in which the ball 216is accommodated is formed in the surfboard body 100, and the ball 216 isaccommodated inside the groove 112. Then, in order to prevent the ball216 from being separated from the groove 112, an anti-separation cover217 is coupled to the surfboard body 100 so that the first propulsionbody 210 is coupled to the surfboard body 100 in a ball-socket jointmethod.

As the first propulsion body 210 is coupled to the surfboard body 100 ina ball-socket joint manner, the surfboard body 100 is enabled to performthe motion of widening or narrowing the first propulsion body 210 in thehorizontal direction on the water surface, the motion of elevating thefirst propulsion body 210 up and down with respect to the surfboard body100, and the motion of rotating the first propulsion body 210 left andright with respect to the surfboard body 100.

Meanwhile, a first propulsion unit 220 is formed in the first propulsionbody 210 in order to generate propulsion force in the first propulsionbody 210 by moving the user's feet. The first propulsion unit 220 isformed on the lower surface of the first propulsion body 210, the firstpropulsion unit 220 is formed in a thin plate shape, and the firstpropulsion unit 220 is formed inclinedly with respect to the lowersurface of the first propulsion body 210. In one embodiment of thepresent invention, the first propulsion unit 220 may be formed in ashape tilted with respect to the axial direction of the first propulsionbody 210 when viewed in a plan view.

On the lower surface of the first propulsion body 210 on which the firstpropulsion unit 220 is formed, an accommodating unit for accommodatingthe first propulsion unit 220 by folding may be formed when thesurfboard 600 is not in use.

The second propulsion body 260 is formed in a rectangular shape, thesecond propulsion body 260 is disposed in a concave groove 110 formed onthe other side of the surfboard body 100, and the second propulsion body260 is formed in a shape in close contact with the groove 110.

In one embodiment of the present invention, the second propulsion body260 may be formed in substantially the same shape and the same size asthe first propulsion body 210.

The second propulsion body 260 may be formed, for example, in arectangular shape or a streamlined shape, and the second propulsion body260 may be formed in a width suitable for placing a user's foot.

On the upper surface of the second propulsion body 260, a strap 265 forpreventing the user's feet from being separated may be formed, and onthe upper surface of the second propulsion body 260, an anti-slip padand the like for preventing the user's feet from slipping may bedisposed. Unlike this, a concave separation prevention groove may beformed in a portion of the upper surface of the second propulsion body260 corresponding to the strap 265 so that the user's foot does notslip.

In one embodiment of the present invention, a ball 266 is formed at thefront end portion of the second propulsion body 260 to enable the userto perform the motion of widening or narrowing the second propulsionbody 260 in the horizontal direction on the water surface, the motion ofelevating the second propulsion body 260 up and down with respect to thesurfboard body 100, and the motion of rotating the second propulsionbody 260 left and right with respect to the surfboard body 100.

Meanwhile, the surfboard body 100 is formed with a concave groove 114 inwhich the ball 266 is accommodated, and the ball 266 is accommodatedinside the groove 114. Then, to prevent the ball 266 from beingseparated from the groove 114, an escape prevention cover 267 is coupledto the surfboard body 100, so that the second propulsion body 260 iscoupled to the surfboard body 100 in a ball-socket joint manner.

As the second propulsion body 260 is coupled to the surfboard body 100in a ball-socket joint manner, the surfboard body 100 is enabled toperform the motion of widening or narrowing the second propulsion body260 in the horizontal direction on the water surface, the motion ofelevating the second propulsion body 260 up and down with respect to thesurfboard body 100, and the motion of rotating the second propulsionbody 260 left and right with respect to the surfboard body 100.

Meanwhile, a second propulsion unit 270 is formed in the secondpropulsion body 260 in order to generate propulsion force in the secondpropulsion body 260 by moving the user's feet. The second propulsionunit 270 is formed on the lower surface of the second propulsion body260, the second propulsion unit 270 is formed in a thin plate shape, andthe second propulsion unit 270 is formed inclinedly with respect to thelower surface of the second propulsion body 260.

In one embodiment of the present invention, the second propulsion unit270 may be formed in a shape tilted with respect to the axial directionof the second propulsion body 260 when viewed in a plan view.

On the lower surface of the second propulsion body 260 on which thesecond propulsion unit 270 is formed, an accommodating unit foraccommodating the second propulsion unit 270 by folding may be formedwhen the surfboard 600 is not in use.

When the user moves the first propulsion body 210 and the secondpropulsion body 260 connected to the surfboard body 100 with their feet,the surfboard body 100 can be advanced even without wind or waves, andin one embodiment of the present invention, the direction change unit300 is coupled to the surfboard body 100 so that the user can change thedirection of the surfboard body 100 that is being advanced by using thehand.

The direction change unit 300 comprises a rotating shaft 310, a handle320, and a direction change key 330. In one embodiment of the presentinvention, the direction change unit 300 may further include, asillustrated in FIG. 4 , a folding unit 340 that allows the rotatingshaft 310 and the direction change key 330 to be folded.

FIG. 4 is a cross-sectional view illustrating a direction change unit.

Referring to FIG. 4 , the folding unit 340 comprises a through hole 342penetrating through the surfboard body 100, a rotating member 344, afirst folding part 346, and a second folding part 348.

The rotating member 344 is formed in a cylindrical block shape, beingrotated inside the through hole 342, and of course, the rotating member344 has a structure not to be separated out of the through hole 342.

A first folding part 346 coupled to the rotating shaft 310 is formed onthe upper surface of the rotating member 344. The first folding part 346includes plates formed to stand up as a pair on the upper surface of therotating member 344, and a rotating shaft 310, which will be describedlater, is inserted between the first folding parts 346, and the firstfolding part 346 and the rotating shaft 310 are coupled by a hinge pin.

The rotating shaft 310 is, for example, formed in a cylindrical shape,and the rotating shaft 310 is hinge-coupled to a hinge pin in a statedisposed between the first folding parts 346.

When the rotating shaft 310 is twisted while the rotating shaft 310 iscoupled to the hinge pin, the rotating member 344 is rotated by thetorsional moment of the rotating shaft 310. Meanwhile, the rotatingshaft 310 may be folded in a vertical state or a horizontal state withrespect to the surfboard body 100 by a hinge pin.

The handle 320 is coupled to the upper end of the rotation shaft 310,and the handle 320 allows the user to change the direction by twistingthe rotation shaft 310 with a less force.

The direction change key 330 is coupled to the lower surface of therotating member 344 by a second folding part 348, and the directionchange key 330 can be folded vertically or horizontally with respect tothe surfboard body 100 by the second folding part 348.

Meanwhile, the direction change key 330 is rotated together with therotating member 344, the rotating member 344 is rotated by the rotatingshaft 310, and since the rotation shaft 310 is rotated by the handle320, as the user rotates the handle 320, the direction change key 330 isalso rotated with the handle 320 so that the user can change thedirection of the surfboard body 100 by hand.

Referring back to FIG. 1 , in one embodiment of the present invention,the upper surface of the surfboard body 100 may be formed with a groove120 formed in a shape and size corresponding to the direction changeunit 300, and as a result, the direction change unit 300 is accommodatedin the groove 120 while being folded, thereby preventing an increase involume due to the direction change unit 300.

Referring back to FIGS. 1 and 2 , the overturn prevention body 400prevents the surfboard body 100 from being overturned and allows theuser to more easily maintain the balance. In the case of the skilled, itis not necessary to deploy the overturn prevention body 400, but in thecase of a beginner or intermediate user, it is possible to preventfalling down on the water surface by deploying the overturn preventionbody 400.

The overturn prevention body 400 is hinged coupled to the front end partof the upper surface of the surfboard body 100 at a different heightfrom the first and second propulsion bodies 210 and 260 so that theinterference with the first and second propulsion bodies 210 and 260 canbe prevented.

For example, the overturn prevention body 400 is disposed on the uppersurface of the surfboard body 100, and the first and second propulsionbodies 210 and 260 may be disposed at positions corresponding to thesides of the surfboard body 100.

Although in one embodiment of the present invention, the overturnprevention body 400 disposed on the upper surface of the surfboard body100 is illustrated and described, but unlike this, the overturnprevention body 400 may be disposed on the lower surface of thesurfboard body 100.

The overturn prevention body 400 may include a first overturn preventionbody 410 and a second overturn prevention body 420.

The first overturn prevention body 410 formed in a rectangular shape isdeployed to one side of the surfboard body 100, and the second overturnprevention body 420 formed in a rectangular shape is deployed to theother side facing the one side of the surfboard body 100.

FIG. 5 is a cross-sectional view illustrating the coupling of anoverturn prevention body and a surfboard body according to an embodimentof the present invention.

Referring to FIG. 5 , the front end part of the first and secondoverturn prevention bodies 410 and 420 of the overturn prevention body400 is formed with a through hole, the front end part of the surfboardbody 100 has a pair of protrusions 102 formed to be spaced apart areformed. The first and second through holes formed at the ends of theoverturn prevention bodies 410 and 420 are inserted into the protrusions102, due to this, the first and second overturn prevention bodies 410and 420 are rotated in the horizontal direction with respect to thesurfboard body 100.

Referring back to FIG. 1 , in order to minimize the volume of thepropulsion body 200 to facilitate storage and transport when thesurfboard 600 is not in use, a first coupling portion 218 that isseparated or coupled to the side of the surfboard body 100 is formed inthe first and second propulsion bodies 210 and 260, and a secondcoupling portion 103 coupled to the first coupling portion 218 is formedin the surfboard body 100.

For example, the first coupling part 218 may be a protrusion, and thesecond coupling part 103 may be a groove into which the protrusion isinserted and fitted.

Meanwhile, in order to minimize the volume of the overturn preventionbody 400 to facilitate storage and transport when the surfboard 600 isnot in use, a third coupling part 402 that is separated or coupled tothe to the upper surface of the surfboard body 100 is formed, and afourth coupling part 105 coupled to the third coupling part 402 isformed on the upper surface of the surfboard body 100.

For example, the third coupling part 402 may be a protrusion, and thefourth coupling part 105 may be a groove coupled to the third couplingpart 402.

FIG. 6 is an external perspective view of surfboards moved by user poweraccording to another embodiment of the present invention. The surfboardmoved by user power illustrated in FIG. 6 has substantially the sameconfiguration as the surfboard moved by user power illustrated anddescribed in FIGS. 1 to 5 except for the third and fourth overturnprevention bodies 430 and 440. Therefore, duplicate descriptions of thesame components will be omitted, and the same names and referencenumerals will be given to the same components.

Referring to FIG. 6 , the overturn prevention body 400 of the surfboardmoved by user power according to another embodiment of the presentinvention may include a third overturn prevention body 430 and a fourthoverturn prevention body 440.

The third overturn prevention body 430 and the fourth overturnprevention body 440 are hinge-coupled at a different height from thefirst and second propulsion bodies 210 and 260 on one side and the otherside of the rear end part of the upper surface of the surfboard body 100so that it is possible to prevent interference with the first and secondpropulsion bodies 210 and 260.

For example, the third overturn prevention body 430 and the fourthoverturn prevention body 440 are disposed on the upper surface of thesurfboard body 100, and the first and second propulsion bodies 210 and260 may be disposed at positions corresponding to the sides of thesurfboard body 100.

Although in one embodiment of the present invention, the third overturnprevention body 430 and the fourth overturn prevention body 440 disposedon the upper surface of the surfboard body 100 are illustrated anddescribed, but unlike this, the third overturn prevention body 430 andthe fourth overturn prevention body 440 may be disposed on the lowersurface of the surfboard body 100.

The third overturn prevention body 430 formed in a rectangular shape isdeployed to one side of the surfboard body 100, and the fourth overturnprevention body 440 formed in a rectangular shape is deployed to theother side facing the one side of the surfboard body 100.

A through hole is formed in the front end part of the third and fourthoverturn prevention bodies 430 and 440, and a pair of protrusions 102spaced apart from each other is formed at the rear end part facing thefront end part of the surfboard body 100 is formed. The through holesformed in the front end part of the third and fourth overturn preventionbodies 430 and 440 are inserted into the protrusions 102, and due tothis, the third and fourth overturn prevention bodies 430 and 440 arerotated in the horizontal direction with respect to the surfboard body100.

Meanwhile, to minimize the volume of the overturn prevention body 400 tofacilitate storage and transport when the surfboard 600 is not used, athird coupling part 402 that is separated or coupled to the uppersurface of the surfboard body 100 is formed in the third and fourthoverturn prevention bodies 430 and 440, and a fourth coupling part 105coupled to the third coupling part 402 is formed on the upper surface ofthe surfboard body 100.

For example, the third coupling part 402 is a protrusion, and the fourthcoupling part 105 may be a groove coupled to the third coupling part402.

The third and fourth overturn prevention bodies 430 and 440 prevent thesurfboard body 100 and the user from overturning backwards and make iteasier for users to balance. In particular, when all of the first tofourth overturn prevention bodies 410, 420, 430, and 440 are used, it ispossible to easily maintain a balance on the water surface, so evenbeginners in surfing can easily enjoy surfing.

In particular, the user can selectively deploy and use the first tofourth overturn prevention bodies 410, 420, 430, and 440 according tothe user's skill level. For example, only the first and second overturnprevention bodies 410 and 420 coupled to the front end part of thesurfboard body 100 or the third and fourth overturn prevention bodies430 and 440 coupled to the rear end part of the surfboard body 100 canalso be optionally deployed and used.

According to the detailed description above, it is possible to move bythe user power on a sea coast where there are no winds or waves,direction can be easily changed by using user's hands while moving, andthere is an effect that each part can be folded to improve theconvenience of moving and minimize the storage volume.

Meanwhile, the embodiments disclosed in the drawings are merelypresented as specific examples to aid understanding, and are notintended to limit the scope of the present invention. It is obvious tothose of ordinary skill in the art to which the present inventionbelongs that other modified embodiments based on the technical spirit ofthe present invention can be implemented in addition to the embodimentsdisclosed herein.

What is claimed is:
 1. Surfboards moved by user power comprising: asurfboard body streamlined, when viewed from a plan view, concavegrooves are formed on both sides, respectively; a propulsion bodyincluding: a first propulsion body formed with a first propulsion unitthat is hinged to one side groove of the surfboard body and is formedinclined with respect to the surfboard body on a lower surface togenerate propulsion force according to the movement of the user's feet;and a second propulsion body formed with a second propulsion unit thatis hinged to the other side groove of the surfboard body and is formedinclined with respect to the surfboard body on a lower surface togenerate propulsion force according to the movement of the user's feet;and a direction change unit including: a rotating shaft passing throughthe surfboard body; a handle disposed on an upper end of the surfboardbody of the rotating shaft to rotate the rotating shaft; and a directionchange key that is disposed on a lower part of the surfboard body of therotating shaft and rotates together with the rotating shaft, wherein thedirection change unit of surfboards moved by user power comprises athrough hole passing through the surfboard body, a rotating memberinserted into the through hole and rotated in a direction parallel tothe surfboard body, a first folding part coupled to the rotating shafton an upper portion of the rotating member to fold the rotating shaft,and a folding unit having a second folding part for folding thedirection change key on a lower portion of the rotating member.
 2. Thesurfboards moved by user power according to claim 1, further comprising:an overturn prevention body having a first prevention body hinged to oneside of the front end part of an upper surface of the surfboard body ofthe surfboards moved by user power and at a different height from thefirst propulsion body; and a second overturn prevention body hinged tothe other side of a front end part at a different height from the firstpropulsion body, wherein the first and second overturn prevention bodiesare coupled to the upper surface of the surfboard body, and wherein thefirst and second propulsion bodies are formed at the same height as theside surface of the surfboard body.
 3. The surfboards moved by userpower according to claim 2, wherein the first and second propulsionbodies of the surfboard moved by user power are hinged in a ball-socketjoint method that freely moves with respect to the surfboard body, andwherein through holes are formed in the first and second overturnprevention bodies, and the through holes are inserted into theprotrusions protruding from the upper surface of the surfboard body sothat the first and second overturn prevention bodies are rotated in adirection parallel to the upper surface of the surface board body. 4.The surfboards moved by user power according to claim 2, wherein a firstcoupling portion that is separated or coupled to the side of thesurfboard body is formed in the first and second propulsion bodies ofsurfboards moved by user power, and a second coupling portion separatedor coupled to the first coupling portion is formed on the side of thesurfboard body, and wherein a third coupling portion coupled to theupper surface of the surfboard body is formed in the first and secondoverturn prevention bodies, and a fourth coupling portion coupled to thethird coupling portion is formed on the upper surface of the surfboardbody.
 5. The surfboards moved by user power according to claim 1,further comprising: an overturn prevention body including a thirdoverturn prevention body that is hinge-coupled at a different heightfrom the first propulsion body on one side of the rear end part facingthe front end part of the upper surface of the surfboard body and afourth overturn prevention body hinged to the other side of the rear endpart at a different height from the first propulsion body, whereinthrough holes are formed in the third and fourth overturn preventionbodies, and the through holes are inserted into the protrusionsprotruding from the upper surface of the surfboard body so that thethird and fourth overturn prevention bodies are rotated in a directionparallel to the upper surface of the surfboard body.